<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>红绿灯</title>
</head>
<body>
    <div>
        <span>1</span>
        <span>2</span>
        <span>3</span>
        </div>
        <style>
        div {
        width: 500px;
        height: 500px;
        background-color: green;
        display: flex;
        justify-content: space-around;
        align-items: center;
        }
        div span {
        width: 150px;
        height: 100px;
        background-color: red;
        }
        </style>
</body>
</html>